1. Technical Field
The present invention relates to transducers for use in a position sensor and in particular, transducers for use in a dual type position sensor which can sense targets both capacitively and inductively.
2. Related Art
Computer devices are well known and significant research has been made into man machine interfaces that allow humans to interact with the computer devices. For example, capacitive touch pads are well known that allow a user to move a cursor around a screen by moving their finger over the touch pad. Touch screens and digitizers are also well known which can be mounted on or under the surface of the display and which allow the user to make selections directly on the display using either their finger or an electromagnetic stylus.
Recently, a number of proposals have been made to provide a sensor that can sense both the user's finger and an electromagnetic stylus using the same sensing device. Some of these systems effectively employ two separate sensors mounted on top of each other over or under the display. U.S. Pat. No. 5,231,381 is an example of such a system. Others have proposed combining the inductive and capacitive sensing elements by using the same conductors for both capacitive and inductive position measurements. WO2004/070396 describes an example of such a combined sensor which uses the same conductor tracks for both inductive and capacitive measurements.